Cobalt is a promising fill material used, for example, as a PMOS fill material in a metal gate, a contact fill, and as a fill material for interconnects. However, the inventors have observed that the deposition of cobalt material onto a substrate results in cobalt residue forming onto process chamber components (such as a process kit that surrounds the substrate). For example, typically, cobalt deposition is performed on several substrates, followed by cooling down and venting of the process chamber. After the process chamber has been cooled and vented, process kit parts having cobalt residue are removed and replaced. After replacement with clean process kit parts, the chamber can be readied for further processing. However, the foregoing sequence of events results in significant down time for the process chamber.
Accordingly, the inventors have developed improved techniques for etching cobalt metal using fluorine radicals.